System and method for welding thermoplastic components to create composite structure

ABSTRACT

A system and method for welding thermoplastic components by positioning and moving a heated plate between the components to melt their respective faying surfaces, and as the plate moves, pressing the components together so that the melted faying surfaces bond together as they cool and re-solidify, thereby creating a composite structure. The plate has a heated portion which is positioned between and heated to melt a portion of the first and second faying surfaces. A manipulator mechanism moves the plate along an interface from between the portion to between a series of subsequent portions of the first and second faying surfaces, thereby welding the thermoplastic components along the entire interface to create the composite structure. The heated portion may contact the faying surfaces and melt them through conduction, or may be suspended between them and melt them through radiation and convection.

RELATED APPLICATIONS

The present U.S. non-provisional patent application is a continuationand claims priority benefit of an earlier-filed U.S. non-provisionalpatent application with the same title, Ser. No. 16/874,069, filed May14, 2020, and an earlier-filed U.S. non-provisional patent applicationwith the same title, Ser. No. 16/013,420, filed Jun. 20, 2018. Theentire contents of the identified earlier-filed applications areincorporated by reference as if fully set forth herein.

FIELD

The present invention relates to systems and methods for creatingcomposite structures, and more particularly, embodiments concern asystem and method for welding thermoplastic components by positioningand moving a heated plate element between the components to melt therespective faying surfaces, and as the plate element moves, pressing thecomponents together so that the melted faying surfaces bond together asthey cool and re-solidify, thereby creating a composite structure.

BACKGROUND

Thermoplastics are polymers, typically synthetic resins, that melt whenheated and solidify when cooled. Thermoplastic laminate components canbe welded by heating and then cooling faying surfaces between thecomponents to bond them together to form composite structures. The mostcommon techniques for thermoplastic composite welding are inductionwelding, ultrasonic welding, and resistance welding, but each of thesetechniques suffers from particular disadvantages.

Induction welding using a susceptor involves incorporating a foreignmaterial into the weld line, which has undesirable effects on structuralintegrity and reliability. Induction welding without using a susceptorcan be difficult to control and requires substantial engineering anddesign to determine the correct coil and heat sink configuration toavoid temperature control problems and resin degradation or poor welds.Further, nearby metal, such as a lightning strike protection conductor,can act as a susceptor and cause additional heat distribution issues.Ultrasonic welding requires an energy director in the weld line, resultsin lower strength welds, can distort fiber alignment, and is difficultto use for continuous welds. Resistance welding using a carbon fiberresistive element in the weld line creates continuous welds with goodstrength. However, resistance welding is difficult to use in productionprocesses because the entire resistance circuit is heated simultaneouslyand therefore must be clamped and supported throughout the entirewelding process. Further, provisions for making reliable electricalbonds to the fibers are not conducive to automation, and individuallocations are not temperature controlled, and instead, the entirecircuit is on a single channel. Further, it is generally important toavoid degrading/deconsolidating the laminate components due tooverheating, so techniques that generate too much heat beyond the fayingsurfaces may require heat mitigation (e.g., heat sink technology).

Traditional hot plate welding is another common technique in which anentire weld area is heated at the same time with a contoured plate andthen the melted surfaces are brought together. However, this can resultin difficulty initially aligning and thereafter maintaining thepositions of the thermoplastic components due to the instability of themelted faying surfaces. It is also known to weld the seams of productsmade of thermoplastic fabrics, such as tents, tarps, and parachutes.However, the nature of the materials makes this welding processsubstantially different than materials welded using the techniquesdescribed above. In particular, the fabrics are much more flexible andare initially separated and brought together at the time of welding,while the materials at issue are relatively stiff (one may even be astiffener structure) and are already aligned and maintained inparticular positions at the time of welding.

This background discussion is intended to provide information related tothe present invention which is not necessarily prior art.

SUMMARY

Embodiments address the above-described and other problems andlimitations by providing a system and method for welding thermoplasticcomponents by positioning and moving a heated plate element between thecomponents to melt the respective faying surfaces, and as the plateelement moves, pressing the components together so that the meltedfaying surfaces bond together as they cool and re-solidify, therebycreating a composite structure.

In one embodiment, a system is provided for welding a firstthermoplastic component to a second thermoplastic component along aninterface to create a composite structure. Broadly, the system mayinclude a plate element and a manipulator mechanism. The plate elementmay have a heated portion which may be positioned between a portion of afirst faying surface of the first thermoplastic component and a secondfaying surface of the second thermoplastic component. The heated portionmay be heated to an operating temperature which is sufficient to meltthe portion of the first and second faying surfaces. The manipulatormechanism may move the plate element along the interface from betweenthe portion of the first and second faying surfaces, which then cool andbond together, to between a series of subsequent portions of the firstand second faying surfaces, and thereby weld the first thermoplasticcomponent to the second thermoplastic component along the interface tocreate the composite structure.

Various implementations of this embodiment may include any one or moreof the following features. The heated portion the plate element may havea thickness of approximately between 0.01 inches and 0.03 inches. Theheated portion of the plate element may be heated using joule heating.The system may further include a first temperature sensor which maydetermine the operating temperature of the plate element, and a secondtemperature sensor which may determine an adjacent temperature of thefirst and second thermoplastic components.

In a first or “contact” implementation, at least the heated portion ofthe plate element may be in physical contact with the portion of thefirst and second faying surfaces, and may melt the portion of the firstand second faying surfaces through conduction. A front portion of theplate element may have a rake angle to control any excess meltedthermoplastic material from the first and second faying surfaces. Therake angle may be approximately between 10 degrees and 50 degrees.

In a second or “gap” implementation, at least the heated portion of theplate element may be suspended between and not in physical contact withthe portion of the first and second faying surfaces, and may melt theportion of the first and second faying surfaces through radiation andconvection. The system may further include a spacer element which maycreate a gap between the first and second faying surfaces, wherein atleast the heated portion of the plate element is located in the gap. Thespacer element may be an unheated front portion of the plate element,and/or the spacer element may include one or more circular rollers. Thesystem may further include an air nozzle configured to introduce astream of air or inert gas between at least the heated portion of theplate element and the first and second faying surfaces so as to enhanceconvection and reduce oxidation. The system may further include one ormore holes in the plate element to enhance convection.

The manipulator mechanism may further include a guide roller configuredto guide movement of the plate element along the interface between thefirst and second faying surfaces. The manipulator mechanism may furtherinclude a pressure roller configured to press the first and secondfaying surfaces together behind the plate element as the plate elementis moved along the interface. The manipulator mechanism may furtherinclude a cooling nozzle configured to deliver a cooling fluid toaccelerate cooling of the first and second faying surfaces behind theplate element as the plate element is moved along the interface. Themanipulator mechanism may further include an inert gas nozzle configuredto deliver an inert gas to displace oxygen around the heated portion ofthe plate element. The system may further include a support surfaceconfigured to be positioned behind the second thermoplastic component,wherein the support surface is flexible so as to accommodate adeflection of the second thermoplastic component as the plate element ismoved between the first and second faying surfaces.

This summary is not intended to identify essential features of thepresent invention, and is not intended to be used to limit the scope ofthe claims. These and other aspects of the present invention aredescribed below in greater detail.

DRAWINGS

Embodiments of the present invention are described in detail below withreference to the attached drawing figures, wherein:

FIG. 1 is a fragmentary cross-sectional side elevation view of anembodiment of a system for welding first and second thermoplasticcomponent to create a composite structure, wherein the system is shownin a starting position;

FIG. 2 is a fragmentary cross-sectional side elevation view of thesystem of FIG. 1, wherein the system is shown moving along an interfacebetween the first and second thermoplastic components;

FIG. 3 is a fragmentary cross-sectional side elevation view of a firstor “contact” implementation of the system of FIG. 1;

FIG. 4 is a fragmentary cross-sectional side elevation view of a secondor “gap” implementation of the system of FIG. 1;

FIG. 5 is an isometric view of an implementation of the system of FIG.1, wherein a plate element component of the system is supported on bothsides;

FIG. 6 is a fragmentary cross-sectional isometric view of the system ofFIG. 5;

FIG. 7 is a fragmentary cross-sectional side elevation view of thesystem of FIG. 5;

FIG. 8 is a fragmentary cross-sectional front elevation view of thesystem of FIG. 5;

FIG. 9 is an isometric fragmentary view of the system of FIG. 5 showingthe plate element component in operation;

FIG. 10 is a plan view of the plate element component of FIG. 5 showinga rake angle;

FIG. 11 is a fragmentary isometric view of an implementation of thesystem of FIG. 1, wherein a plate element component of the system issupported on one side (i.e., cantilevered);

FIG. 12 is a fragmentary cross-sectional front elevation view of thesystem of FIG. 11;

FIG. 13 is an isometric fragmentary view of the system of FIG. 11showing the plate element component in operation;

FIG. 14 is a plan view of the plate element component of FIG. 11 showinga rake angle;

FIG. 15 is a fragmentary cross-sectional side elevation view of thesystem of FIG. 5;

FIG. 16 is a fragmentary front elevation view of a roller elementcomponent of the system of FIG. 15; and

FIG. 17 is a flowchart of steps involved in a method of welding firstand second thermoplastic component to create a composite structure,wherein the system is shown in a starting position.

DETAILED DESCRIPTION

The following detailed description of embodiments of the inventionreferences the accompanying figures. The embodiments are intended todescribe aspects of the invention in sufficient detail to enable thosewith ordinary skill in the art to practice the invention. Otherembodiments may be utilized and changes may be made without departingfrom the scope of the claims. The following description is, therefore,not limiting. The scope of the present invention is defined only by theappended claims, along with the full scope of equivalents to which suchclaims are entitled.

In this description, references to “one embodiment”, “an embodiment”, or“embodiments” mean that the feature or features referred to are includedin at least one embodiment of the invention. Separate references to “oneembodiment”, “an embodiment”, or “embodiments” in this description donot necessarily refer to the same embodiment and are not mutuallyexclusive unless so stated. Specifically, a feature, structure, act,etc. described in one embodiment may also be included in otherembodiments, but is not necessarily included. Thus, particularimplementations of the present invention can include a variety ofcombinations and/or integrations of the embodiments described herein.

Broadly characterized, embodiments provide a system and method forwelding thermoplastic components by positioning and moving a heatedplate element between the components to melt the respective fayingsurfaces, and as the plate element moves, pressing the componentstogether so that the melted faying surfaces bond together as they cooland re-solidify, thereby creating a composite structure. In contrast totraditional hot plate welding which heats the entire weld area at thesame time, embodiments utilize the motion of the plate element and thestiffness of the components and/or an underlying support surface toprovide a clamping force against the plate element to join the meltedsurfaces. Further, unlike in traditional hot plate welding, there may belittle or no movement of the components themselves because the fayingsurfaces are kept together and are only separated by the thin plateelement moving between them during the welding process. Althoughdescribed herein in the example context of manufacturing aircraft, thepresent technology may be adapted for use in substantially any suitableapplication (in, e.g., the automotive and/or ship-building industries)involving welding thermoplastic components.

Referring initially to FIGS. 1 and 2, an embodiment of a system 20 isshown for welding a first thermoplastic component 22 to a secondthermoplastic component 24 to construct a composite structure 26. In oneexample application, the first component 22 may be an aircraft stringeror other relatively rigid component, and the second component may be anaircraft skin or other relatively flexible component. The system 20 mayinclude a plate element 28 and a manipulator mechanism 30. The plateelement 28 may be configured to be positioned between an initial orcurrent portion 32 a of a first faying surface 34 of the firstthermoplastic component 22 and a second faying surface 36 of the secondthermoplastic component 24, and to be heated to an operating temperaturewhich is sufficient to melt the portion 32 a of the first faying andsecond faying surfaces 34,36.

The thickness of the plate element 28 may depend, at least in part, onthe natures of the first and/or second components 22,24 and theparticular application and requirements of the welding process. Ingeneral, it may be desirable for the plate element 28 to be relativelythin so as to minimize the deflection of the first and/or secondcomponents 22,24 as the plate element 28 moves between them. Relatedly,the maximum ability of the first and/or second component 22,24 todeflect may determine an upper limit on the thickness of the plateelement 28. In various implementations, the plate element 28 may have athickness of approximately between 0.005 inches and 0.05 inches,approximately between 0.01 inches and 0.03 inches, or approximately 0.02inches. The thickness of the plate element 28 may also depend, at leastin part, on the nature and design of the manipulator mechanism 30 whichsupports the plate element 28. For example, a cantilevered plate elementmay be relatively thicker to avoid buckling, while a plate elementsupported on both ends may be relatively thinner. The plate element 28may be constructed of substantially any suitable material, such asnichrome, titanium, Inconel, stainless steel, or other high temperature,corrosion resistant metal. In one implementation, the plate element 28may be constructed of a material having a relatively high electricalresistance to facilitate joule (or resistance) heating.

The plate element 28 may be heated by one or more heating circuits. Morespecifically, the plate 28 may be joule heated to an operatingtemperature by passing an electric current through the material of theplate. The operating temperature of the plate 28 may depend, at least inpart, on the natures of the first and/or second components 22,24 and theparticular application and requirements of the welding process. Ingeneral, the operating temperature may be sufficient to melt the firstand second faying surfaces 34,36 and accomplish the desired weld. Thus,the minimum operating temperature may be the melting point of the firstand second faying surfaces 34,36, and the maximum temperature may bedetermined by the ability to transfer enough heat sufficiently quicklyso to avoid degradation/decomposition of the first and second components22,24 due to the heat. In particular, it may be desirable to heat thefirst and second faying surfaces 34,36 while minimizing heating of thebodies of the first and second components 22,24.

The temperature of the plate element 28 may be measured by one or morefirst sensors 40 (shown in FIGS. 3 and 4) at one or more locations onthe plate element 28. Multiple measurements at different points may bedesirable if the plate element 28 loses more heat in one region than inanother region due to, e.g., a heat sink effect. In one implementation,one or more thermocouples may be used to measure the temperature of theplate element 28. Relatedly, multiple independently controllable heatingcircuits may be used to heat the plate element 28 to better compensatefor any such differences in temperature across the plate element 28, andto allow for greater flexibility in how the faying surfaces 34,36 areheated. The temperature of the first and second faying surfaces 34,36may be at least as relevant as the temperature of the plate element, inwhich case the temperature of the first and second faying surfaces 34,36may be measured by one or more second sensors 42 (shown in FIGS. 3 and4) at one or more locations on the faying surfaces 34,36. In oneimplementation, one or more optical temperature sensors may be used tomeasure the temperature of the first and second faying surfaces 34,36.

In one implementation, additional resin may be introduced and meltedbetween the faying surfaces 34,36 to facilitate bonding. This additionalresin may be provided in the form of injected liquid resin, solid resinfilm, or an additional layer of prepreg (i.e., an extra layer of fiberand resin).

In a first or “contact” implementation, shown in FIG. 3, the plateelement 28 may be generally in physical contact with the faying surfaces34,36 while the plate element 28 moves between and heats the fayingsurfaces 34,36 through conduction. In the contact implementation, afront portion 44 of the plate element 28 may be provided with a rakeangle to direct or otherwise control any excess thermoplastic resinmaterial from the first and second faying surfaces 34,36. Morespecifically, the rake angle may sweep the excess resin to thecenterline of the weld where it may be squeezed out of the way, whichpromotes the ejection of air from between the first and secondcomponents 22,24. In various implementations, the rake angle may beapproximately between 10 degrees and 50 degrees, or approximatelybetween 20 degrees and 40 degrees.

In a second or “gap” implementation, shown in FIGS. 4, 15, and 16, theplate element 28 may be generally suspended between and not in physicalcontact with the faying surfaces 34,36 as the plate element 28 movesbetween and heats the faying surfaces 34,36 through radiation andconvection. In the gap embodiment, a spacer element 46 may be providedto create a gap in which at least the heated portion of the plateelement 28 moves, and thereby prevents the faying surfaces 34,36 fromphysically contacting at least this heated portion of the plate element28. In one implementation, the spacer element 44 may be provided bythickening or shaping an unheated front portion of the plate element 28to separate the faying surfaces 34,36 around the heated portion of theplate element 28. In another implementation, the same spacing effect maybe accomplished by physically forcing (e.g., pulling or pushing) thefirst and/or second faying surfaces 34,36 apart. In anotherimplementation, a wedge or roller element 48 may be provided at theleading edge of the plate element 28 to create the gap. As shown in FIG.16, the roller element 48 may include a plurality of rollers which maybe offset from each other so that some of the rollers 54 roll across thefirst faying surface 34 and others of the rollers 56 roll across thesecond faying surface 36. Such as roller element advantageously avoidsdragging across and potentially damaging or contaminating the fayingsurfaces 34,36. One advantage of the gap embodiment is that it avoidsphysical, high temperature contact which could otherwise damage ormisalign the fibers of the first and second thermoplastic components.However, the gap embodiment may require a higher operating power thanthe contact embodiment due to convection heat losses. In variousimplementations, an air nozzle 80 may introduce air into the gapsbetween the plate element 28 and the faying surfaces 34,36 to enhanceconvection, and/or one or more holes 82 may be provided in the plateelement 28 itself to enhance convection.

Referring also to FIGS. 5-15, the manipulator mechanism 30 may beconfigured to move the heated plate element 28 between the first andsecond faying surfaces 34,36, from one end of the interface 58 of thefirst and second components 22,24 to the other end, such that the plateelement 28 heats and melts the portion 32 a of the first and secondfaying surfaces 34,36, and such that as the plate element 28 is movedalong the interface 58, the heated and melted portions of the first andsecond faying surfaces 34,36 bond together as they cool and re-solidifybehind the plate element 28. The manipulator mechanism 30 may supportthe plate element 28 on both sides of the plate element, as shown inFIGS. 5-10, or may support the plate element 28 only on one side (i.e.,cantilevered), as shown in FIGS. 11-14. The manipulator mechanism 20 maymove the plate element 28 at a rate of movement that maintains the plateelement 28 in position for a sufficient time to heat the faying surfaces34,36 to the melting temperature. The movement rate may be substantiallycontinuous or potentially variable in order to better maintainparticular temperatures. The rate of movement may depend on such factorsas the operating temperature of the plate element 28 and the rate ofheat transfer from the plate element 28 to the faying surfaces 34,36.Further, the manipulator mechanism 30 may move the plate element 28 at aspeed that maintains the operating temperature with the available poweror may adjust the power to support the desired movement speed in aclosed control loop such that the peak temperature (plate temperature)and the adherend surface temperature after the passage of the plateelement 28 are both within the appropriate temperature range forobtaining a strong weld without degrading the thermoplastic components22,24.

The manipulator mechanism 20 may further include a guide roller 62configured to guide movement of and ensure desired positioning of theplate element 28 between the first and second faying surfaces 34,36. Inone implement, the guide roller 62 may roll over a surface of one of thecomponents 22,24. The first and second components 22,24 may bepositioned by tooling, or the manipulator mechanism 30 may include aguidance feature to position one of the components relative to theother. In one implementation, the manipulator mechanism 20 may furtherinclude a compliance spring, arm, or cylinder or similar complianceelement 64 configured to maintain the guide roller 62 in contact withthe surface of the component 22,24 as the plate element 28 is moved.Relatedly, the system 20 may further include one or more temporary orpermanent fasteners 66 a,66 b positioned at the extreme ends of thefirst and second components 22,24 as desired or necessary to maintainthe component 22,24 in proper alignment, though permanent fasteners maylimit how closely the weld can approach these ends.

In one implementation, the manipulator mechanism 30 may use onlylocalized pressure applied by the manipulator mechanism 30 because themass of the material being heated is less than with most other weldingmethods and no foreign material is being introduced. In anotherimplementation, the manipulator mechanism 30 may further include apressure roller 70 configured to press the melted first and secondfaying surfaces 34,36 together behind the plate element 28 as the plateelement 28 is moved along the interface 58 by the manipulator mechanism30, thereby facilitating the bonding together of the cooling first andsecond faying surfaces 34,36. The pressure applied by the pressureroller 70 may depend on the nature of the first and second components22,24. In particular, stiffer components may require greater pressure.In one implementation, the pressure applied by the pressure roller maybe at least 1 bar.

In one implementation, the manipulator mechanism 20 may further includea cooling nozzle 72 configured to deliver a cooling fluid, such ascompressed air, refrigerant, or water, may be impinged against the firstand second components 22,24 to accelerate cooling as desired ornecessary. In one implementation, the manipulator mechanism 20 mayfurther include an inert gas nozzle 74 configured to deliver an inertgas into the weld area in order to displace the oxygen in the weld areaand thereby reduce the potential for oxidation and/or fire during theheating and consolidating phases. In one implementation, the system 20may further include a support surface 76 position beneath, behind, orotherwise adjacent to the second component 24. The support surface 76may be compressible or otherwise flexible so as to accommodate adeflection of the second component 24 as the plate element 28 movesbetween first and second faying surfaces 34,36. For example, in theexample application in which the first component is a stringer and thesecond component is a skin, because the skin is much more flexible thanthe stiffener, the skin may be placed on the support surface 76, and thesupport surface 76 may compress or otherwise flex to accommodate thedeflection of the skin, while also providing a constant reaction forceagainst the plate element 28 and the melted weld line. The supportsurface 76 may itself rest upon a flat or contoured tool 78.

Referring to FIG. 17, the system 20 may function substantially asfollows to weld the first thermoplastic component 22 to the secondthermoplastic component 24 along the interface 58 to create thecomposite structure 26. Additional functionality of the system 20 may bereflected in the steps of the method 200 discussed below. Broadly, theheated portion of the plate element 28 may be positioned between theportion 32 a of the first faying surface 34 of the first thermoplasticcomponent 22 and the second faying surface 36 of the secondthermoplastic component 24, as shown in 222. The heated portion may beheated to the operating temperature which is sufficient to melt thematrix of the first and second faying surfaces 34,36, as shown in 224.The manipulator mechanism 30 may move the heated portion of the plateelement 28 along the interface 58 from between the portion 32 a of thefirst and second faying surfaces 34,36 to between the series ofsubsequent portions 32 b-32 e of the first and second faying surfaces34,36, as shown in 230. As the plate element 28 is moved along theinterface 58, the portion of the first and second faying surfaces 34,36behind the plate element 28 is no longer exposed to the operatingtemperature and so begins to cool and re-solidify and bond together, asshown in 236, which results in the first thermoplastic component 22being welded to the second thermoplastic component 24 along theinterface 58 to create the composite structure 26.

The system 20 may include more, fewer, or alternative components and/orperform more, fewer, or alternative actions, including those discussedelsewhere herein, and particularly those discussed in the followingsection describing the method 220.

Referring again to FIG. 17, an embodiment of a method 220 is shown forwelding a first thermoplastic component 22 to a second thermoplasticcomponent 24 along an interface 58 to create a composite structure 26.The method 220 may be a corollary to the functionality of the system 20described above, and may be similarly implemented using the variouscomponents of the system 20. Broadly, the method 220 may proceedsubstantially as follows.

A heated portion of a plate element 28 may be positioned between aportion 32 a of a first faying surface 34 of the first thermoplasticcomponent 22 and a second faying surface 36 of the second thermoplasticcomponent 24, as shown in 222. The heated portion may be heated to anoperating temperature which is sufficient to melt the matrix resin ofthe portion 32 a of the first and second faying surfaces 34,36 withoutexceeding a decomposition temperature of the first and second components22,24, as shown in 224. The heated portion may be heated by jouleheating or by substantially any other suitable technique, and theresulting heat may be transferred to the portion 32 a of the first andsecond faying surfaces 34,36 by conduction or radiation or convection.In an implementation in which heat is transferred from the plate element28 to the first and second faying surfaces 34,36 by convection, an airnozzle 80 or similar mechanism may be used to introduce a stream of airor other inert gas between at least the heated portion of the plateelement 28 and the first and second faying surfaces 34,36 so as toenhance convection and/or reduce oxidation, as shown in 226. In oneimplementation, an inert gas nozzle 74 or similar mechanism may be usedto deliver an inert gas to displace oxygen around the heated portion ofthe plate element 28, as shown in 228.

A manipulator mechanism 30 may move the heated portion of the plateelement 28 along the interface 58 from between the portion 32 a of thefirst and second faying surfaces 34,36 to between a series of subsequentportions 32 b-32 e of the first and second faying surfaces 34,36, asshown in 230. As the plate element 28 is moved along the interface 58,the portion of the first and second faying surfaces 34,36 behind theplate element 28 is no longer exposed to the operating temperature andso begins to cool and re-solidify and bond together, as shown in 236,which results in the first thermoplastic component 22 being welded tothe second thermoplastic component 24 along the interface 58 to createthe composite structure 26. In one implementation, a guide roller 62 orsimilar mechanism may be used to guide movement of the plate element 28along the interface 58 between the first and second faying surfaces34,36, as shown in 232.

A first temperature sensor 40 may be used to determine the operatingtemperature of the heated portion of the plate element 28, and a secondtemperature sensor 42 may be used to determine a temperature of thefirst and second thermoplastic components 22,24, as shown in 234, andthis information may be used to control the heating of the heatedportion of the plate element 28 and the speed with which the manipulatormechanism 30 moves the heated portion along the interface 58.

In one implementation, a pressure roller 70 or similar mechanism may beused to apply a pressure to press the cooling first and second fayingsurfaces 34,36 together behind the plate element 28 to enhance bondingas the plate element 28 is moved along the interface 58, as shown in238. In one implementation, a cooling nozzle 72 or similar mechanism maybe used to deliver a cooling gas or other fluid to accelerate cooling ofthe first and second faying surfaces 34,36 behind the plate element 28to hasten re-solidification and bonding as the plate element 28 is movedalong the interface 58, as shown in 240.

The method 220 may include more, fewer, or alternative actions,including those discussed elsewhere herein.

Although the invention has been described with reference to the one ormore embodiments illustrated in the figures, it is understood thatequivalents may be employed and substitutions made herein withoutdeparting from the scope of the invention as recited in the claims.

Having thus described one or more embodiments of the invention, what isclaimed as new and desired to be protected by Letters Patent includesthe following:

1. A system for welding a first thermoplastic composite component to a second thermoplastic composite component along an interface to create a composite structure, the system comprising: a plate comprising a heated portion positioned between a portion of a first faying surface of the first thermoplastic component and a second faying surface of the second thermoplastic component, the heated portion being heated to a temperature which is sufficient to melt the portion of the first and second faying surfaces; a manipulator mechanically coupled with the plate and moving the plate along the interface from between the portion of the first and second faying surfaces, which then cool and bond together, to between a series of subsequent portions of the first and second faying surfaces; and a support surface positioned against the second thermoplastic composite component, the support surface being flexible so as to accommodate a flexing of the second thermoplastic composite component due to the plate positioned and moving between the portion of the first and second faying surfaces.
 2. The system of claim 1, wherein the first thermoplastic composite component is a stiffener and the second thermoplastic composite component is a skin.
 3. The system of claim 1, the heated portion the plate comprising a thickness of between 0.01 inches and 0.03 inches.
 4. The system of claim 1, the heated portion of the plate being heated using joule heating.
 5. The system of claim 1, further comprising a first temperature sensor determining the operating temperature of the plate, and a second temperature sensor determining an adjacent temperature of the first and second thermoplastic composite components.
 6. The system of claim 1, at least the heated portion of the plate being in physical contact with the first and second faying surfaces, and melting the first and second faying surfaces through conduction.
 7. The system of claim 6, a front portion of the plate comprising a rake angle to control any excess melted thermoplastic material from the first and second faying surfaces, and the rake angle being between 10 degrees and 50 degrees.
 8. The system of claim 1, at least the heated portion of the plate being suspended between and not in physical contact with the first and second faying surfaces, and melting the first and second faying surfaces through radiation and convection.
 9. The system of claim 8, further comprising a spacer creating a gap between the first and second faying surfaces, and at least the heated portion of the plate being located in the gap.
 10. The system of claim 8, further comprising an air nozzle introducing a stream of air between at least the heated portion of the plate and the first and second faying surfaces so as to enhance convection.
 11. The system of claim 8, further comprising one or more holes in the plate to enhance convection.
 12. The system of claim 1, the manipulator further comprising a guide roller guiding movement of the plate along the interface between the first and second faying surfaces.
 13. The system of claim 1, the manipulator further comprising a pressure roller pressing the first and second faying surfaces together behind the plate as the plate is moved along the interface.
 14. The system of claim 1, the manipulator further comprising a cooling nozzle delivering a cooling fluid to accelerate cooling of the first and second faying surfaces behind the plate as the plate is moved along the interface.
 15. The system of claim 1, the manipulator further comprising an inert gas nozzle delivering an inert gas to displace oxygen around the heated portion of the plate.
 16. A method for welding a first thermoplastic composite component to a second thermoplastic composite component along an interface to create a composite structure, the method comprising: aligning the first and second thermoplastic composite components along the interface, such that a first faying surface of the first thermoplastic composite component is in contact with a second faying surface of the second thermoplastic composite component; positioning a plate between a portion of the first faying surface and the second faying surface; heating at least a portion of the plate to a temperature which is sufficient to melt the portion of the first and second faying surfaces; and moving the plate with a manipulator mechanically coupled with the plate in a direction along the interface from between the portion of the first and second faying surfaces, which then cool and bond together, to between a series of subsequent portions of the first and second faying surfaces, such that the first faying surface remains in contact with the second faying surface in front of and behind the plate relative to the direction the plate is moving.
 17. The method of claim 16, wherein the first thermoplastic composite component is a stiffener and the second thermoplastic composite component is a skin, and the skin flexes away from the stiffener at the portion of the first and second faying surfaces to accommodate the plate.
 18. The method of claim 17, wherein the manipulator is positioned proximate to the skin, and the skin flexes away from the stiffener.
 19. The method of claim 17, wherein the manipulator is positioned proximate to the stiffener, and the skin flexes away from the stiffener.
 20. A method for welding a thermoplastic composite stiffener to a thermoplastic composite skin along an interface to create a composite structure, the method comprising: aligning the thermoplastic composite stiffener and the thermoplastic composite skin along the interface, such that a first faying surface of the thermoplastic composite stiffener is in contact with a second faying surface of the thermoplastic composite skin; positioning a plate between a portion of the first faying surface and the second faying surface; heating at least a portion of the plate to a temperature which is sufficient to melt the portion of the first and second faying surfaces; moving the plate with a manipulator mechanically coupled with the plate in a direction along the interface from between the portion of the first and second faying surfaces, which then cool and bond together, to between a series of subsequent portions of the first and second faying surfaces, such that the first faying surface remains in contact with the second faying surface in front of and behind the plate relative to the direction the plate is moving; and supporting the thermoplastic composite skin with a support surface, the support surface being flexible so as to accommodate a flexing of the thermoplastic composite skin due to the plate positioned and moving between the portion of the first and second faying surfaces 